Polyelectrolyte-Coated Cerium Oxide Nanoparticles: Insights into Adsorption Process

We investigated ceria nanoparticle/strongly charged polyelectrolyte solution interface on the example of adsorption of a strong polyelectrolyte poly(sodium 4-styrenesulfonate), PSS, on cerium oxide nanoparticles to quantitatively characterize the above-mentioned interface. The obtained results could enable a better prediction of nanoparticles behavior in polyelectrolyte solution which could lead to improved applications of ceria nanoparticles. We initially both synthetized and characterized ceria nanoparticles. For the characterization X-ray powder diffraction (XRD), bright-field scanning transmission electron microscopy (TEM), dynamic light scattering (DLS), and electrophoretic mobility measurements were used. Results revealed that nanoparticles are spherical with primary ceria nanoparticles diameter (nanocrystallite size) of approximately 3.5 nm. Results of high-resolution TEM, DLS, and electrophoretic mobility measurements after adsorption of PSS showed that polyelectrolyte-coated nanoparticles were obtained. The comparison of average hydrodynamic diameters of uncoated and PSS-coated ceria nanoparticles leads to the assumed thickness of the polyelectrolyte layer of δ ≈ 9 nm. Finally, for the quantitative interpretation of polyelectrolyte adsorption on ceria nanoparticles, the application of the modified Ohshima model was examined. In that respect, the adsorption parameters such as charge density of the polyelectrolyte layer electrophoretic softness and adsorption density were determined. It was thus shown that Ohshima model could be applied for studying ceria nanoparticle/strongly charged polyelectrolyte solution interface and that the obtained results could serve as a basis for further tailored applications of polyelectrolytes as stabilizing agents for nanoparticles.